How to Change the Coolant in a 1985 Honda CR250

Shop parts for a 1985 Honda CR250 Dirt Bike.

Changing the coolant in your 1985 Honda CR250 is essential for maintaining optimal engine temperature and preventing corrosion inside your cooling system. This model uses a liquid-cooled two-stroke engine, which requires regular coolant changes–ideally at least once per year or after heavy riding seasons. The 1985 CR250's aluminum cylinder and radiator make it especially important to use the correct type of coolant to avoid internal corrosion and overheating.

What You'll Need

  • New ethylene glycol-based coolant (pre-mix or mix with distilled water, avoid silicate-based formulas)
  • 10mm socket or wrench
  • Drain pan
  • New water pump crush washer (optional, but recommended)
  • Clean rags
  • Protective gloves

Caution for 1985 CR250 Owners

The 1985 CR250 has an aluminum radiator and engine components. Always use ethylene glycol coolant, never plain water or car-only/fleet coolants—these can damage the aluminum. Double-check hose integrity; the age of this bike means hoses may become brittle and more likely to leak under pressure. Inspect for cracks before reassembly.

Drain the Old Coolant

  • Allow the bike to cool completely. Removing coolant from a hot engine is dangerous and can cause burns.
  • Remove the seat and fuel tank for easier access to the radiator cap and hoses.
  • Place a drain pan below the water pump (left side of the engine).
  • Remove the 10mm drain bolt at the bottom of the water pump. Allow old coolant to fully drain into the pan. If available, replace the crush washer before reinstallation for a leak-free seal.
  • Slightly loosen the radiator cap to allow air in–this speeds draining and prevents vacuum lock. Do not fully remove the cap until all pressure is gone.

Flush the System (Recommended)

  • Reinstall the drain bolt temporarily and fill the radiator with distilled water.
  • Start the engine and let it idle for 1–2 minutes. Turn it off before overheating.
  • Remove drain bolt again and let the water exit. Repeat if necessary until water runs clear.

Refill with New Coolant

  • Ensure the drain bolt is securely installed (with new washer if possible).
  • Pour the new coolant mixture into the radiator slowly until it reaches the top of the filler neck.
  • Check the overflow (expansion) tank and fill to its marked level.
  • Replace radiator cap securely.

Bleed Air Out of the System

  • Start the engine and let it run briefly with the radiator cap off (be careful of possible splashes). Add more coolant if the level drops.
  • Squeeze the radiator hoses by hand–this helps purge trapped air bubbles.
  • Once coolant remains steady at the filler neck, replace the cap.
  • Check the overflow tank level and adjust as needed.

Final Checks

  • Inspect all hose connections, drain bolt, and radiator cap area for leaks while idling and after a short ride.
  • An overheat warning or low coolant after your first ride signals a possible air bubble or a leak–let the engine fully cool and top up the radiator as necessary.

Maintenance Notes Specific to the 1985 CR250

  • The 1985 radiators are more prone to age-related internal corrosion–never let the system run dry, and always keep it filled with fresh coolant.
  • Radiator fins are delicate. While working, avoid bending them–this diminishes cooling performance.
  • If you notice persistent coolant loss, check the water pump seal and hoses. These parts can deteriorate after decades and may require replacement.

Consistent coolant changes will keep your Honda CR250 running cool and reliable. Don't forget to inspect all cooling system parts regularly to avoid unexpected issues.

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Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.